Vehicle charging inlets include receptacle assemblies for connecting a charging cable from an external power source to a vehicle harness connected directly or indirectly to a vehicle battery. Amongst other circuits, the interface between the charging cable and the receptacle assembly connects the vehicle battery to the electrical grid using AC power line wires to facilitate battery charging. The receptacle assembly can include an internal printed circuit board (PCB) for connecting wires from the vehicle harness to male terminals or pins, which mate with corresponding terminals in the charging cable connector. To provide overcurrent protection at the vehicle side, the vehicle harness may include fuses connected to the wire harness' AC power lines. The fuses help protect vehicle wiring during long-term, unattended charging operations. The fuses are typically connected to the AC power lines downstream from the charging inlet. In some applications, the fuses are integrated with the PCB at the charging inlet.
The charging receptacle is exposed to harsh automotive environments (e.g., water, salt, hot and cold temperatures, sunlight, etc.), particularly when the vehicle is driven, and needs to be sealed to protect internal high voltage (HV) circuits from contamination. Because the HV circuits require substantial isolation between ground, neutral and phase lines, any internal circuit design at the charging receptacle needs to include complete sealing from surrounding environments. The PCB is one flat plane with little to no isolation of components. Utilization of the PCB or some other circuit design with traces (e.g., system of bus bars, flexible circuit, or the like) requires the insulator applied during the manufacturing process (e.g., conformal coating, potting materials, etc.) to be void of micro-contamination. If water gets into the receptacle assembly, the internal circuit provides a water leak path at the pins potentially creating short circuits across the PCB. Indeed, under HV conditions, the presence of humidity can bridge the short distances between traces and create a high resistive short condition.
Moreover, during the charging process, the fuses heat up and are cooled down when charging is completed. The fluctuation in fuse temperatures creates thermal stress to the fuse carriers (e.g., PCB, busbar system, or flexible circuit) and to the insulating potting material possibly causing potential separation of the materials and potential leak paths.